Answer 1

Look up the answers posted for this question:

" Difference between "one-way function" and "cryptographic hash function" "
https://crypto.stackexchange.com/questions/8773/difference-between-one-way-function-and-cryptographic-hash-function

Hope this helps.
Happy Coding!

Answer 2

There is no practical way to recover the input from the output, hence, it is only one way. Also, two different inputs may result in same output, so, which one do you chose to recover in that scenario? It may be the other one.